Temermostatic switch



June 20, 1933. L. SATCHWELL 1,914,676

THERMOSTATIC SWITCH Filed March 4, 1931 I 3 Sheets-Sheet 1 G wbw; #MM

June 20, 1933. L SATCHWELL THERMQSTATIC SWITCH Filed March 4, 1931 3 Sheets-Sheet 2 June 20, 1933. R L. 'SATCHWELL THERnos'rATIb SWITCH 3 Sheets-Sheet 5 Filed March 4, 1931 43 the base of the switch.

Patented June 20,. 1933 UNITED STATES LEONARD SATCHWELL,

or snouen, nnemiim THERMOSTATIC SWITCH:

Application filed March 4,

This invention relates to thermostatic switches in which a bi-metallic strip carries one of the contacts of the circuit making and breaking device, a magnet being used to en sure a flick action of the switch. More particularly the invention is concerned with thermostatic switches of the. type described in my U. S. Patent 1,7 98,854, granted March 31, 1931. The invention has for its oh set to provide an improved construction of thermostatic switch of this type.

A feature of the invention consists in the provision in association with t -e iii-metallic strip of a shunting strip in parallel there- 1 with proportioned to carry some oi cur rent passing through the switch so as to reduce the amount of current carried by the bi-metallic strip and thus prevent the heat- I ing thereof by the current.

Other features of the invention will here inafter appear.

Two embodiments of the invention are illustrated in the accompanying drawings, Figs. 1 to 3 illustrating one embodiment and Figs. 4 and 5 a second embodiment, Figs.

- 6 and 7 being detail views hereinafter referred to.

Fi l is an elevation of the thermostatic switc with the cover removed, 2 an eleso vation with the cover in position, Fig. 3 is a side view with the cover in section.

Fig. 4 is a side View of a second embodiment with the cover in section, while Fig. 5 is an elevation with the cover section.

Figs. 6 and 7 show detail views of the manner of supporting the contact.

The embodiment illustrated 3 dilfers irom that shown in i and h principally in this that in l. to 3 the chassis or frame supporting the various elements of the thermostatic switch is disposed at right angles to the base while in the construction shown in Figs. 4 and h the chassis or frame elements are disposed parallel to Referring now to both embodiments, 1 indicates a chassis. or framework supporting .the elements of the thermostatic switch and 2 indicates the base of the switch which may be of metal and to which the chassis 1 is shown) 1931. Sierial No. 520,123.

connected by screws 3, mica or other insu lating washers 4 serving to insulate the chassis 1 from the base 2 and from the screws 3. On the chassis or framework 1 is secured by screws 5 a horseshoe or other magnet fiwhich is insulated from the chassis by means of mica insulation 7. Between the poles of the magnet 6 is fitted a contact 8 adapted to cooperate with a contact 9 provided on an armature 10 carried by a bi metallic strip 11. The bi-metallic strip 11 is secured by screws 12 to a pivoted support 13 which is held on its pivot it and is also pressed against an adjusting screw 15 by means of a spring 16.

- In the emhodimentshown in Figs. 1 to 3 the pivot it is constituted by a pin connecting the flanges of the chassis l which is of channel form, while in Figs. t and 5 the pivot it is constituted by lugs en aging in notches i8 iormed on upstanding lugs 19 on the chassis. To the bi-metallic strip 11 is connected adjacent the armature 10 a copper or other metal strip 20 connected at its other end to the chassis l and adapted to carry a portion of the total current which is passed through the switch contacts 8 and 9 when the circuit through them is closed. An

arm 4&0 is mounted upon the frame by means of the same screws that hold the magnet in place, and this arm carries an adjustable stop screw 23 to limit the travel of the moving armature 10 and contact 9 to such an amount when in the open position the gap between the contacts 8 and 9 is onlysuflicient to safely withstand the potential difierence existing between the contacts when open.

in the embodiment shown in Figs. 1 to 3 the contact 8 is connected to a terminal 21 by means of a plate 22 and the lei-metallic strip 11 and junction strip (29 are connected through the chassis l to the other terminal by way of terminal fixing screws (not upon a hloch 24 of insulating material aiiixed to the base. In the above embodiment the arm 40 is insulated from the magnet lay a sheet of insulation 7 and the stop 23 is shown as being used as a third contact which is con- The terminals are all mounted,

nected by a plate 41 with a third terminal 25. In the embodiment shown in Figs. 4 and 5 the contact 8 is connected to the terminal 21 by means of a plate 26 while the bi-metallic strip 11 and junction strip 20 are connected with the other terminal 21a. by means of a plate 27.

An adjusting screw 15 which serves to adjust the initial position of the bi-metallic strip is fitted with a toothed wheel 28 and a knob 29 is provided with a pin 30 which is arranged to engage with the toothed wheel 28. i

This arrangement provides a convenient means of calibrating the instrument as the pin 30 may be brought into engagement between any pair of teeth on the wheel 28. After calibration the knob 29 and adjusting screw 15 are locked together and can be rotated as one unit to vary the operating temperature. A stop 31 is provided to engage with a stop 32 on the knob 29 to prevent the adjustment being operated beyond the limits of the scale.

Contact 8 is supported by being threaded into a plate 33 mounted on the magnet, and I may be adjusted by screwing it into or out of the plate. The contact is also threaded through a second plate 34 parallel to the first and fastened thereto by small screws 35. By tightening the small screws and drawing the plates closer together, the contact is locked in position and cannot be turned to screw or unscrew it. This structure is shown in detail in Figures 6 and 7.

In the instrument shown in Figs. 1, 2 and 3 a scale is carried by the knob 29 and rotates with it opposite a fixed indicating pointer 36 on the cover 37, while in the instrument shown in Figs. 4 and 5 the knob 29 forms an indicating pointer rotating within a fixed scale 38 mounted on cover 39.

I claim,

1. A thermostatic switch comprising a base, switch elements, a chassis carrying said switch elements, said chassis supported on but insulated from the base, a magnet secured to but insulated from the chassis, a contact embraced by the poles of the magnet, a support pivoting about the chassis, a bi-metallic strip secured to said support, a contact carried by said strip adapted to cooperate with the contact embraced by the poles of the magnet, a connection between a source of current and said bi-metallic strip, an adjusting screw rotatable in said chassis and serving to vary the position of the bimetallic strip for adjustment of the temperature at which the bi-metallic strip will operate the switch element and a metal junction strip connected to the bi-metallic strip adjacent the contact carried thereby and connected in parallel with said bi-metallic strip and serving to carry a predetermined proportion of the total current traversing the switch.

2. A thermostatic switch comprising a base, switch elements, a chassis carrying said switch elements, said chassis supported on but insulated from the base at right angles thereto, a magnet secured to but insulated from the chassis, a contact embraced by the poles of the magnet, a support pivoting about the chassis, a bi-metallic strip secured to said support, a contact carried by said strip adapted to co-operate with the contact embraced by the poles of the magnet, a connection between a source of current and said bi-metallic strip, an adjusting screw rotatable in said chassis and serving to vary the position of the bi-metallic strip for adjustment of the temperature at which the bimetallic strip will operate the switch element and a metal junction strip connected to the bi-metallic strip adjacent the contact carried thereby and connected in parallel With said bi-metallic strip and serving to carry a predetermined proportion of the total current traversing the switch.

3. A thermostatic switch comprising a base, switch elements, a chassis carrying said switch elements, said chassis supported on but insulated from the base and disposed parallel to said base, a magnet secured to but insulated from the chassis, a contact embraced by the poles of the magnet, a support pivoting about the chassis, a bi-metallic strip secured to said support, a contact carried by said strip adapted to co-operate with the contact embraced by the poles of the magnet, a connection between a source of current and said bi-metallic strip, an adjusting screw rotatable in said chassis and serving to vary the position of the bi-metallic strip for adjustment of the temperature at which the bi-metallic strip will operate the switch element and a metal junction strip connected to the bi-metallic strip adjacent the contact carried thereby and connected in parallel with said bi-metallic strip and serving to carry a predetermined proportion of the total current traversing the switch.

4. A thermostatic switch comprising a base, switch elements, a chassis carrying said switch elements, said chassis supported on but insulated from the base, a magnet secured to but insulated from the chassis, a contact embraced by the poles of the magnet, means permitting adjustment of the position of the contact between the poles of the magnet and locking the contact, said means comprising a screwed portion engaged by the contact and a locking plate adjustable by means of screws in relation to the screwed portion engaged by said contact, a support pivoting about the chassis, a bimetallic strip secured to said support, a contact carried by said stri adapted to 00-01)- erate with the contact embraced by the poles of the magnet, a connection between a source of current and said bi-metallic strip, an adjusting screw rotatable in said chassis and serving to vary the position of the time tallic strip for adjustment of the temperature at which the bi-metallic strip Will operate the switch element, and a metal junction strip connected to the lei-metallic strip adjacent the contact carried thereby and connected in parallel with said bi-metallic strip and serving to carry a predetermined proportion of the total current traversing the switch.

In testimony whereof I have signed my name to this specification.

LEONARD SATCHWELL. 

